Wideband Power Meter
If you are looking for the Wideband Power Meter, click here to purchase and learn more.
NEVER CONNECT A RADIO TRANSMITTER THAT EXCEEDS +20 dBm (100mW) AS THIS IS THE MAXIMUM POWER ALLOWED INTO THE DEVICE. EXCEEDING THIS RATING MAY CAUSE DAMAGE TO THE POWER METER, YOUR COMPUTER AND THE TRANSMITTING DEVICE. IF YOU DO NOT KNOW THE POWER OUTPUT LEVEL OR THERE IS A CHANCE IT WILL EXCEED THE RATING, USE AN ATTENUATOR!
For your convenience, we sell a 20dB attenuator at our store. This is an extremely high quality, genuine attenuator from Mini-Circuits, a world leader in RF components.
The Wideband Power Meter can be used to measure the power level from just about any radio source! You can measure the total RF output from QRP rigs, programmable oscillators, DDS IC's, home brew amplifiers, HamShields, bluetooth or WiFi modules and just about anything else.
Reading the measurement is simple. Just connect to any computer and use your favorite terminal program. Don't have a favorite yet? You can check out the following:
|Arduino Serial Monitor||X||X||X|
SparkFun also has a great write up on terminal programs that you can find here.
Mac OSX and Linux require no driver installation. Windows 10 should automatically recognize the device as a serial port.
Identifying the Serial Port
OSX: your terminal program should show the serial device in the listing
Linux: type in ls /dev/*tty* and look for the USB serial device. If there are multiple, try unplugging the power meter, listing the directory, and plugging it in to identify what changed.
Windows: Simply search for "Device Manager" in your search bar, and click "Ports (COM & LPT)" for details. You will see something like this:
Sometimes computers have a variety of ports listed, but "USB Serial Device (COM8)" is the device in my case. You can unplug, hit F5 (refresh), and see if it disappears. Plug it in again, hit F5 (refresh), which may give you a clue as to what it is.
Still having driver issues? Does it show up as an unknown device? We have a few solutions at the bottom of this article.
Device Baud Rate
The device transmits data at 9600 8N1. This is an extremely common (and likely default) baud rate.
Once you have established connection, you will see the device list out the current received signal strength on a new line every second, such as this when it is connected to nothing:
-34.43 -34.91 -34.98 -34.84 -34.50 -33.55 -34.98 -34.91 -34.98 -33.76 -34.84 -34.98 -34.91 -32.61 -34.98 -34.77 -34.91
This is the instantaneous signal strength for that second. I have nothing plugged in and this is what the lowest level looks like.
Note: Make sure that your transmitter transmits a steady signal for AT LEAST a couple of seconds, as bursty transmissions will be averaged out. For complex data devices, use the CW regulatory test mode (FCC Test Mode), as it will perform best.
VHF-SHF Power Measurements
These measurements are extremely well calibrated and within the specifications of the chip. It ranges from 39-2700MHz and is a moderately flat +/- 1dB after calibration.
HF Power Measurements
We have performed extensive testing on its lower frequency response. We wanted to give the HF QRP community something low cost and accurate. While not perfect, its generally well within specifications. This is not only useful for amateur radio operators, but folks experimenting with HIFER and 49ER unlicensed bands! Yes, there are FCC Part 15 unlicensed HF bands out there. You can learn more here: http://www.lwca.org/sitepage/part15/index-what.htm
HF Error Plot
This is the error plot from measuring frequencies below 39MHz. Note that we can reliabilty obtain power readings within a dB or two down to 10MHz. While it still can be a benchmark for lower frequencies, its not very accurate. Don't worry though, we are working on a 0Hz-10MHz variant so we can help folks out in the VLF bands, VLF free band (LowFER), lower amateur radio HF bands, and MedFER.
Using Frequency Calibration Table
While the device allows the user to freely input any RF, we have also added the ability to the firmware to accept the target frequency in order to provide exact correction data.
To set the target frequency, type "F", the frequency in MHz, and enter. For example: F50<enter> sets the frequency to 50MHz. F15<enter> sets it to 15MHz.
Gerbers, Schematics, Firmware and Instructions
The Wideband Power Meter is Open Hardware! We put everything here:
Additional Windows Driver Options
The Power Meter board is automatically recognized as a USB serial device under OSX and Linux, however, windows requires a driver to associate the device with the built in USB serial device drivers.
When first attaching the device to a windows based host, windows will attempt to find a driver and fail. You may then specify a driver. This is provided in ERD_RF_Power_Meter.inf.
Once you have installed the driver, the Power Meter will register as a COM port device under windows, and you may access it with any serial/terminal application of your preference.
During the driver installation process on Windows 8 operating systems and above you may encounter "The third-party INF does not contain digital signature information" preventing the installation of the included driver. The steps below outline the process for disabling driver signature enforcement on Windows 8/8.1 systems.
NOTE: If your system uses BitLocker Drive Encryption, you will need your encryption key to gain access to advanced settings to disable driver signature enforcement.
Windows 8 - Navigate to PC settings > General and look for the Advanced startup dialog. Click the Restart now button to access the advanced startup settings. Your system will now reboot.
Windows 8.1 - Navigate to PC settings > Update and Recovery > Recovery and look for the Advanced startup dialog. Click the Restart now button to access the advanced startup settings. Your system will now reboot.
After rebooting select Troubleshoot > Advanced options > Startup Settings, click the Restart button, your machine will reboot a second time.
After rebooting a second time you should be presented with the Windows Startup Settings dialog, choose Disable driver signature enforcement by pressing number
7 on your keyboard. Your machine will reboot automatically.
Once rebooted, you should now be able to install the drviers as outlined above. Once the appropriate driver is selected you will see a Windows Security dialog warning against the installation of the unsigned driver. Click Install this driver software anyway to complete the driver installation.
Advanced Power Meter Commands
There are a few commands that you might find interesting when controlling the power meter. You can type commands at any time on the power meter.
|F<Frequency in MHz>||Set the working frequency and loads the calibration values from EEPROM||F15|
|R<Sample Interval>||Adjusts how frequently the power meter should sample. 1 second is the default. Can only be 1-10.||R2|
|<ESC Key>||Prints the help menu|
|HELP||Prints the help menu|
Debug Power Meter Commands
These commands are probably not useful to the typical user, but here are some additional ones we have added.
WARNING: Some of these commands can do annoying things. Be careful!
|Control ]||Erase the entire EEPROM calibration table. Will repopulate on the next reboot.|
|Control ^||Put the board into DFU mode for programming. Will go back to normal on reboot|
|DEBUG||Prints software version, EEPROM version, EEPROM values, and current calibration values|
|SETSLOPE <SPAN> <VALUE>||This sets the slope value for the given frequency span. The 0-2700MHz range of the device is broken up into 27, 100MHz wide frequency spans for calibration. Span 0 covers 0-99MHz, 1 covers 100-199MHz, etc. Value is expressed as a whole number. IE: 173 is 17.3mV/dBm||SETSLOPE 0 173|
|SETINTERCEPT <SPAN> <VALUE>||Sets the intercept for the given frequency span. Expressed in negative dBm with no sign. IE: 68 is -68 dBm||SETINTERCEPT 0 68|
|OUTPUTRAW||This switches between dBm values and raw voltage measured from the ADC||OUTPUTRAW|